Doubly overload-protected power distribution system

Abstract

A power distribution system consists of an inverter means providing power to a plurality of separate outputs, with each separate output being protected by its own individual overload protection means. In case more than a pre-determined rate of power has been drawn from one of these separate outputs for longer than a pre-determined time, the associated individual overload protection means acts to remove the power from this particular output--without affecting the other outputs. However, if for some reason the individual overload protection means for that particular output fails to operate within the pre-determined time, a second overload protection means operates to disable the inverter, thereby to remove power from all the separate outputs.

I claim: 
     
       1. A power conditioner adapted to be connected with and to be powered from the voltage on an ordinary electric utility power line, comprising: an input circuit connected with said power line and operative to provide an AC voltage at a pair of AC input terminals, said input circuit having a set of control terminals and being operative upon the receipt of a disable signal at said control terminals to substantially diminish the magnitude of said AC voltage; and   a plurality of pairs of AC output terminals, each one of these pairs of AC output terminals having a current sensor and being individually and separately connected with said pair of AC input terminals by way of said current sensor and operable to provide an AC output, said current sensor being: (i) operative to sense the magnitude of the current associated with said AC output, (ii) connected in circuit with said control terminals, and (iii) operable to provide a disable signal to said control terminals in case the magnitude of the current associated with said AC output exceeds a pre-determined level for more than a certain length of time;   whereby, if the magnitude of the current flowing from at least one of said pairs of AC output terminals exceeds said pre-determined level for more than said certain length of time, said AC voltage will substantially diminish in magnitude, thereby reducing the magnitude of the current associated with said AC output.   
     
     
       2. The power conditioner of claim 1 wherein a current-responsive circuit breaker means is connected in circuit with at least one of said separate pairs of AC output terminals and operable to diminish the flow of current from said one pair in case the magnitude of the current flowing therefrom has exceeded a pre-determined over-current protection level for longer than a very brief period of time; whereby, if the current flowing from said one pair of AC output terminals exceeds said over-current protection level for longer than a very brief period of time, the magnitude of the current flowing from said one pair of output terminals will be diminished substantially without affecting the output provided from the other pairs of AC output terminals.   
     
     
       3. The power conditioner of claim 2 wherein said very brief period of time is shorter than said certain length of time. 
     
     
       4. The power conditioner of claim 3 wherein said very brief period of time is on the order of ten seconds or less. 
     
     
       5. The power conditioner of claim 1 wherein said input circuit comprises frequency converter means and wherein the frequency of said AC voltage is substantially higher than that of the voltage on said power line. 
     
     
       6. A power supply adapted to be powered from the voltage on an ordinary electric utility power line and comprising: power distributing means connected with said power line and operative to provide an output voltage at each one of a plurality of separate pairs of power output terminals; and   for each individual one pair of said plurality of separate pairs of power output terminals:   (a) first means responsive to current flowing from said individual one pair of power output terminals and operative to effect a reduction in the magnitude of the voltage provided across said individual pair in case the current drawn therefrom has exceeded a pre-determined magnitude for longer than a brief period of time, said reduction being effected substantially without affecting the magnitude of the voltage provided across the remianing pairs of power output terminals; and   (b) second means also responsive to current flowing from said individual one pair of power output terminals and operative to prevent the magnitude of the current drawn from this individual one pair of output terminals from exceeding said pre-determined magnitude for longer than a short period of time, said short period of time being longer than said brief period of time;   whereby, even if the first means fails, the magnitude of the current available from any one of said plurality of pairs of power output terminals is limited by said second means.   
     
     
       7. The power supply of claim 6 wherein said power distributing means comprises frequency converter means operative to make the frequency of said output voltage substantially higher than that of the voltage on said power line. 
     
     
       8. An over-load protected power distribution system comprising: an input circuit connected with the voltage on an ordinary electric utility power line and operative to provide an AC voltage at a pair of AC input terminals, said input circuit having a set of control terminals and being operative at the receipt of a disable signal at said control terminals to substantially diminish the magnitude of said AC voltage; and   a plurality of pairs of AC output terminals, each one of these pairs of AC output terminals having a current sensing means and being individually and separately connected with said pair of AC input terminals by way of this current sensing means and operable to provide an AC output, said current sensing means being: (i) operative to sense the magnitude of the output current flowing from said AC output, (ii) connected in circuit with said control terminals, and (iii) operable to provide a disable signal to said control terminals in case the magnitude of said output current exceeds a pre-determined level for longer than a certain length of time;   whereby, if the magnitude of the current flowing from at least one of said pairs of AC output terminals exceeds said pre-determined level for longer than said certain length of time, said AC voltage will substantially diminish in magnitude, thereby reducing the magnitude of the current flowing from said AC output.   
     
     
       9. The power distribution system of claim 8 wherein a current-responsive circuit breaker means is connected in circuit with at least one of said separate pairs of AC output terminals and operable to diminish the flow of current from said one pair in case the magnitude of the current flowing therefrom has exceeded a pre-determined over-current protection level for longer than a very brief period of time; whereby, if the current flowing from said one pair of AC output terminals exceeds said over-current protection level for longer than a very brief period of time, the magnitude of the current flowing from said one pair of output terminals will be diminished substantially without affecting the output provided from the other pairs of AC output terminals.   
     
     
       10. The power distribution system of claim 9 wherein said very brief period of time is shorter than said certain length of time. 
     
     
       11. The power distribution system of claim 10 wherein said very brief period of time is on the order of ten seconds or less. 
     
     
       12. The power distribution system of claim 9 wherein said input circuit comprises frequency converter means and wherein the frequency of said AC voltage is substantially higher than that of the voltage on said power line. 
     
     
       13. An arrangement comprising: power supply means having an input connected with an ordinary electric utility power line and a main output operative to provide at each one of plural output receptacles an AC voltage of frequency substantially higher than that of the voltage normally present on the power line, each output receptacle having current-limiting means and current sensing means and being separately and individually prevented from supplying current of magnitude exceeding a predetermined level even if electrical connection is maintained between the main output and any of said output receptacles through said current limiting means; and   a number of individual load means, each individual load means being adapted to be disconnectably connected with and powered by the AC voltage provided at one of the plural separate output receptacles.   
     
     
       14. A power distribution system connected with an ordinary utility power line and mounted to a ceiling, comprising: separate individual power supplies mounted to the ceiling at spaced-apart locations, each power supply being connected with the power line and having a main output and distribution means operative to provide at each one of plural separate individual output receptacles an AC voltage of frequency substantially higher than that of the voltage normally present on the power line, each output receptacle having current-limiting means and current sensing means and being separately and individually prevented from supplying current of magnitude exceeding a predetermined level even if any of said output receptacle maintains electrical connection with said main output and distribution means through said current limiting means; and   a number of separate individual load means, each load means being mounted in support relationship with the ceiling and adapted to be disconnectably connected with and powered by the AC voltage provided at one of the plural output receptacles of one of the power supplies.